1. FIELD OF THE INVENTION
The present invention relates to a ventilator of a distributor for ignition of an engine.
2. DESCRIPTION OF THE PRIOR ARTS
Referring to FIGS. 1, 2 and 3, the conventional distributor will be described.
FIG. 1 shows a distributor having the structure in which a semiconductor amplifying circuit having ignition function is included as a single ignition unit in a housing of the distributor.
In FIG. 1, the reference numeral (1) designates a housing of the distributor which is made of aluminum which has excellent heat radiation property; (2) designates a rotary shaft held by a bearing (3) in the housing (1); (4) designates a cylinder which is freely fitted to the rotary shaft (2); (5) designates a ring signal rotor fitted to the cylinder (4); (6) designates a movable plate which is rotatably held around the rotary shaft (1) to the housing (1); a connecting pin (7) is pivoted at one part of the movable plate and a link (9) of a vacuum leading angle device (8) is freely fitted to the connecting pin (7); (10) designates a stator which is fixed through a permanent magnet (11) on the movable plate (6) and has three projections (10a) which can face to the rotor (5) through each gap. The reference numeral (12) designates a signal unit which is fixed in the housing (1) and which comprises a bobbin (12a) and a pair of supporting parts (12b); (13) designates a metallic cover held between the upper and lower supporting parts (12b). The bobbin (12a) and the supporting parts (12b) are formed in one piece and the metallic cover (13) is partially buried in the one piece. The reference numeral (14) designates a signal coil which is wound on the bobbin (12a) of the signal unit (12); (15) designates a heat sink metallic cover which contains a semiconductor amplifier formed by IC having the ignition circuit function which is partially buried under the ignition unit (not shown); (16) designates a pair of tie screws for fixing the ignition unit and the signal unit (12) in one piece to the housing (1); (17) designates a cam type centrifugal spark advancer leading angle device; (18) designates fitting pieces which are formed at two symmetric places of the centrifugal spark advancer (18); (19) designates a distributor rotor which has a half arm and is fixed to the base of the centrifugal spark advancer (18) and which has an opening (19a) having a size for exposing the ignition unitor; (20) designates a pair of tie screws for fixing the distributor rotor (19) by screwing into the screw holes of the centrifugal spark advancer; (21) designates a rotor electrode fixed on the uppart part of the distributor rotor (19); one end of the rotor electrode is brought into slidably contact with a central electrode (22) and the other end of the rotor electrode sequentially face to peripheral electrodes (23); (24) designates a distributor cap which is fitted and fixed in the housing (1) and on which the central electrode (22) and the peripheral electrodes (23) are fixed; (24a) designates a cylindrical projection molded in one piece in the molding for the distributor cap; (25) designates a ventilation plug made of rubber which comprises fitting part (25a) for fitting to the cyrindrical projection and a cover (25b) so as to perform the ventilation in the distributor housing by the ventilation plug and the water proofing and explosion proofing structure in the housing is formed by the cover (25b). In the conventional ventilator the cylindrical projection is formed in the molding of the distributor cap (24) shown in FIG. 2 and the fitting part (25a) and the cover (25b) of the ventilation plug (25) are simultaneously formed with rubber etc. as shown in FIG. 3; and then, the fitting part (25a) of the ventilation plug (25) is fitted to the cylindrical projections of the distributor cap so as to hold the ventilation plug on the cylindrical projection of the distributor cap by the rubber elasticity.
In the conventional ventilator, the ventilation plug (25) has not satisfactory durability because it is made of rubber and the ventilation plug (25) is held on the distributor cap by only rubber elasticity and accordingly, there is a possibility to detach the ventilation plug after the fitting. It has been proposed to fix the ventilation plug to the ventilation hole formed on the distributor cap by a ultrasonic bonding operation. In the latter structure, the ventilation plug is bonded to the distributor cap and accordingly, the disadvantage of the conventional ventilator for detaching the ventilation plug has not been eliminated. It is possible to consider one piece molding of the ventilation plug in the molding of the distributor cap. Thus, the mold for the distributor cap should have a remarkably complicated configuration whereby it has not been practically employed from the viewpoints of the processability and economy.